Gray cast iron with high austenite to eutectic ratio. Part I. Calculation and experimental evaluation of the fraction of primary austenite in cast iron

The amount of primary austenite at the end of solidification in the microstructure of cast iron has a direct impact on the mechanical properties. However, the large majority of papers discussing the mechanical properties of cast iron relate these properties only to graphite shape. The main reason is the difficulty in correctly assessing the amount of primary austenite in the microstructure. This paper describes two methods of measuring the fraction of primary austenite in cast iron: i) through the use of cooling curve analysis, and ii) through quantitative evaluation of color-etched micrographs. The first method also allows the evaluation of solid fraction evolution along the solidification process, which is validated with quenched (interrupted solidification) gray iron specimens.